Recyclable polymer and process for production thereof

ABSTRACT

A novel resin is provided which is renewable with less energy. A process for renewing the resin is also provided. The present invention includes a polymer having the repeating unit represented by Structural Formula (1) below, and a process for producing the polymer: [—P 1 —R—] n  (1). In the formula, P 1  indicates an addition polymer moiety having a continuous hydrocarbon chain as the skeleton containing no condensation system, and is a polymer or oligomer prepared by addition polymerization of one or more monomers having a double bond; R indicates a linking group constituted of a condensation system for linking the polymer moieties P; and n is a number of repeating units and is an integer of 2 or more.

This application is a division of application Ser. No. 10/443,089, filed May 22, 2003 now U.S. Pat. No. 7,009,007, which is a continuation of International Application No. PCT/JP02/13381, filed Dec. 20, 2002, which claims the benefit of Japanese Patent Application Nos. 389887/2001, filed Dec. 21, 2001, 389895/2001, filed Dec. 21, 2001, and 368037/2002 filed Dec. 19, 2002. All prior applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a novel polymeric material, which can be reused by decomposition and re-synthesis. Also, the present invention relates to a novel process for decomposition-repolymerization of a polymeric material, and to a novel system of material circulation.

2. Related Background Art

Through the years, various novel materials, which are useful in everyday life and industry, have been developed successively by coal chemical techniques and by petrochemical techniques. Typical examples include plastic materials, such as polyethylene, polypropylene, polystyrene and polyvinyl chloride, and rubbers such as polyisoprene and polybutadiene. Recently, resin materials having unique properties have been Developed, such as polyimide resins having excellent heat resistance and high impact strength, and entirely-aromatic liquid crystalline polymers.

However, such polymers are seldom reused. The polymers, after disposal as waste materials, will remain in the environment to impose a heavy burden thereon on a global scale. Waste materials from industrial activities and everyday life are becoming serious as social problems, because of the shortage of dumping sites, undesirable generation of dioxins on incineration, increase in carbon dioxide concentration in the air, and so forth. At the moment, development of materials and products in consideration of the global environment is being anticipated in connection with the carbon dioxide gas emission quotas and waste materials. It is considered to be necessary to develop a technique, which minimizes the consumption of the global resources to maintain the global environment.

In recent years, to meet the above problems, techniques have been developed for reuse of polymeric materials: for example, reuse of plastic parts after simple washing and reworking of used resins for other uses of different added value; a material recycling technique, such as molding of a used resin and a virgin resin in a sandwich state, as described Japanese Patent Publication No. 6-24739; chemical recycling techniques, such as decomposition of a used resin into a monomer after being cut into pieces; and a thermal recycling technique, such as use of waste resin as fuel.

However, of such material recycling techniques, the reuse technique is limited to using the parts in the same capacity. The material recycling technique has problems with the stability of the properties due to the deterioration of the material, guarantee of the products, deterioration of appearance, and so forth. The use of this technique is limited practically to lower grade articles. The chemical recycling technique is limited in the kinds of applicable materials and has problems with the monomer yield. Also, a large amount of energy is required to decompose the polymer into the monomer. The thermal recycling technique has problems of the combustion heat inherent to the material and reduction of carbon dioxide generation. Thus, no recycling technique meets the requirements of the market. To meet these requirements, a novel resin, which can be regenerated using a small amount of energy, and a novel technique for regenerating the resin are wanted.

The resins are classified roughly into condensation polymerization type polymers and addition polymerization type polymers. The condensation polymerization type polymers, which are typified by polyamides, are readily depolymerized at the condensation sites by an acid or base, whereas the addition polymerization type polymers, such as polystyrene, require a large amount of energy for depolymeization in an inert gas atmosphere under a high temperature.

Moreover, the decomposition products contain a mixture of dimers, trimers, tetramers, and so forth, in addition to the monomers, as described in T. Sawaguchi et al., Polym. Int. 49, 921 (2000). From the mixture, only the polymerizable monomer should be isolated, and a large amount of energy is necessary for the isolation. The yield of the recovered monomer is also important. Some of the addition polymerization polymers, such as polypropylene, cannot readily be depolymerized by the above-mentioned method.

Besides, decomposition of plastics using water or carbon dioxide in a supercritical state of a high temperature and a high pressure has been investigated, as described in Japanese Patent Laid-Open No. 8-72058. Such a method is not regarded to be the best from the standpoint of the large-scale treatment and the large amount of energy to be inputted. Therefore, universally applicable techniques are needed.

At the moment, the materials and products, which meet the global environmental problems, such as carbon dioxide gas emission quotas and waste problems, are needed. On the other hand, a reduction in consumption is required to maintain the natural resources.

The conventional addition type polymers, which are synthesized by a monomer addition reaction, can be regenerated for the material circulation only by chemical decomposition into the monomer.

Otherwise, a polymer can be formed from lower polymer molecules shorter in length than the practical polymer molecules as a kind of chemical parts (hereinafter the lower polymer being referred to as a “polymer” occasionally) by introducing a functional group into the parts for linkage-and-decomposition, and synthesizing the polymer from these parts. The polymer after use as an article, such as a molded product, can be returned to the original chemical parts by breaking the linkage between the parts. The recovered parts can be formed again into a polymer by linking the parts together.

Specifically, a polymer that has two condensable functional groups, and a molecule that has two functional groups capable of linking with the above condensable functional groups to serve as a coupler for the polymer, are employed.

An example is provided below using a styrene polymer. A styrene polymer having a carboxyl group on each end of the molecule is employed as the two-functional polymer, and butanediol is employed as the coupling molecule having two functional groups linkable with the above functional groups of the polymer. These compounds are linked together by dehydration condensation in the presence of an acid catalyst to form a high polymer having a structure of successive linkage of the styrene polymer and the butanediol. Each of the styrene polymer moieties and butandiol moieties are linked by ester linkage.

The ester linkage can be broken by a hydrolysis reaction into the original styrene polymer having a carboxyl group at the respective ends and butanediol. Thus, the reaction is reversible. The compounds thus obtained can be converted into a high molecular styrene polymer by the same polycondensation reaction as above repeatedly without limitation of the repetition time.

SUMMARY OF THE INVENTION

[1] The present invention is related to Polymer (A) represented by Structural Formula (1) below: [—P₁—R—]_(n)  (1). In the formula, P₁ indicates an addition polymer moiety having a continuous hydrocarbon skeleton containing no condensation system and formed by addition polymerization of one or more monomers having a double bond; R indicates a linking moiety comprised of a condensation system; and n is a number of repeating units and is an integer of 2 or more.

[2] The present invention is also related to the polymer in Item [1], wherein the linking moiety R is selected from the group consisting of —CO—O—, —CONH—, —NH—CO—O—, and —NH—CO—NH—.

[3] The present invention relates also to the polymer in Item [1], wherein the linkage sites of R represented by the bond between P₁ and R in the repeating unit of Structural Formula (1) are the same throughout the repeating units.

[4] The present invention is also related to the polymer stated in Item [1], wherein the linkage sites of R represented by the bond between P₁ and R in the repeating unit of Structural Formula (1) are different between the adjacent repeating units.

[5] The present invention is also related to the polymer in Item [1], wherein the linkage sites of R represented by the bond between P₁ and R in the repeating unit of Structural Formula (1) are selected at random from the linkage sites of R.

[6] The present invention is also related to the polymer in any of Items [1], [3], [4] and [5], wherein the linking moiety R is represented by Structural Formula (2) below: X1-A—X2  (2). In the formula, X1 and X2 are, respectively, an atomic group linked to P₁ in Structural Formula (1), and A is an atomic group capable of linking with X1 and X2.

[7] The present invention is also related to the polymer in Item [6], wherein X1 and X2 are selected respectively from the group consisting of —CO—O—, —CONH—, —NH—CO—O—, and —NH—CO—NH—.

[8] The present invention is also related to the polymer in Item [6], wherein X1 and X2 are the same atomic group.

[9] The present invention is also related to the polymer in Item [7], wherein the same atomic groups X1 and X2 are respectively —CONH—.

[10] The present invention relates also to the polymer in Item [6], wherein the atomic groups X1 and X2 are different from each other.

[11] The present invention is also related to the polymer in Item [10], wherein the linkage site of X1 and/or X2 to A is selected at random from plural linkage sites of X1 and X2, respectively.

[1′] The present invention is also related to the polymer in Item [10], wherein the linkage sites of X1 and/or X2 to A are the same throughout the repeating units.

[11″] The present invention is also related to the polymer in Item [10], wherein the linkage sites of X1 and/or X2 to A are different from each other in the adjacent repeating units.

[12] The present invention is also related to the polymer in Item [1], wherein the addition polymer moiety P₁ is at least one moiety selected from the group consisting of polystyrene, polybutadiene, polyacrylonitrile, polyethylene and polypropylene.

[13] The present invention is also related to the polymer in Item [6], wherein the group A is an alkylene group.

[14] The present invention is also related to the polymer in Item [13], wherein the alkylene group has a phenyl group on a side chain.

[15] The present invention is also related to the polymer in Item [13], wherein the alkylene group has a phenylene group in the main chain.

[16] The present invention is also related to the polymer in Item [5], wherein the group A is a phenylene group.

In the above description, the depolymerization process for cutting selectively the linkage in the linking moiety R and a process for molding the polymer are assumed to be conducted under relatively mild conditions.

Under severer conditions, the polymer molecules can be cut by various stresses exerted on the polymer molecules in some cases. Such cutting of the molecules does not result in the original two-functional polymer after the hydrolysis, but can provide a molecule having a reactive functional group only on one end of the molecule. Such a molecule serves as a reaction-terminating agent to retard the growth of the molecule, which can prevent formation of a sufficiently high-molecular polymer.

In such a case, a compound (B) is added, which has a condensable functional group and a spin-trapping group. With this compound, when the polymer (A) is cut inside the addition polymer moiety P₁, compound (B) reacts with polymer (A) to introduce the condensable functional group to the end of the molecule of the polymer (A). (Incidentally, the term “polymer” in the present invention is used occasionally for indicating a composition of the polymer represented by Structural Formula (1) containing another substance.)

[17] The present invention is also related to a composition containing, in mixed form, a polymer in Item [1] and a compound having a condensable functional group and a spin-trapping group.

[18] The present invention is also related to the composition in Item [17], wherein the polymer is a condensate of P₁ and R.

[19] The present invention is also related to the composition in Item [17], wherein the compound having a condensable functional group and a spin-trapping group is represented by Structural Formula (3): X₃—M₁—X₄  (3).

In the formula, X₃ is a condensable functional group; X₄ is a spin-trapping group; M₁ is selected from the group consisting of —(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)— (n2, m1 and m2 are, respectively, integers from 1 to 8, and —C₆H₄— represents a phenylene group).

[20] The present invention is also related to the composition in Item [19], wherein the compound having a condensable functional group and a spin-trapping group is a nitroso compound.

[21] The present invention is also related to a molded article formed by molding the polymer in Item [1].

[22] A process for producing the polymer represented by Structural Formula (1), comprising condensation-polymerizing an addition-polymer having a functional group at each end thereof solely or in a manner of making a two-functional compound intervening therebetween: [—P₁—R—]_(n)  (1). In the formula, P₁ indicates an addition polymer moiety having continuous hydrocarbon skeleton containing no condensation system and formed by addition polymerization of one or more monomers having a double bond; R indicates a linking moiety comprised of a condensation system for linking plural P₁ moieties; and n is a number of repeating units and is an integer of 2 or more.

[23] The present invention is also related to the process for producing the polymer in Item [22], wherein the process further comprises adding a compound having a condensable functional group and a spin-trapping group to the polymer represented by the above Structural Formula (1).

[24] The present invention is also related to the process for producing the polymer in Item [23], wherein the polymer represented by the above Structural Formula (1) is one in any of Items [2] to [16], [35], and [36].

[25] The present invention is also related to the process for producing the polymer in Item [23], wherein the compound having the condensable functional group and the spin-trapping group is represented by Structural Formula (3): X₃—M₁—X₄  (3). In the formula, X₃ is a condensable functional group; X₄ is a spin-trapping group; and M₁ is selected from the group consisting of —(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)— (n2, m1, and m2 are, respectively, an integer from 1 to 8).

[26] The present invention is also related to the process for producing the polymer in Item [22], wherein the process further comprises a step of molding the polymer represented by the above Structural Formula (1).

[27] The present invention is also related to a method for treating the polymer comprising a step of providing the polymer represented by Structural Formula (1) below, and a step of depolymerizing the polymer by cutting selectively a linkage in the linking moiety R: [—P₁—R—]_(n)  (1). In the formula, P₁ indicates an addition polymer moiety having a continuous hydrocarbon skeleton containing no condensation system and formed by addition polymerization of one or more monomers having a double bonds; R indicates a linking moiety comprised of a condensation system for linking the plural P₁ moieties; n is a number of repeating units; and is an integer of 2 or more.

[28] The present invention is also related to the method for treating the polymer in Item [27], wherein the method further comprises a step of condensing the substance obtained by the depolymerization into a polymer.

[29] The present invention is also related to the method for treating the polymer in Item [27], wherein the method further comprises a step of molding the polymer obtained.

[30] The present invention is also related to the method for treating the polymer in Item [27], wherein the method further comprises a step of dissolving the polymer in a solvent before the depolymeization step.

[31] The present invention is also related to the method for treating the polymer in Item [27], wherein the linking moiety R is represented by Structural Formula (2) below, and at least one of the bonds of X1 and X2 is cut: X1-A—X2  (2). In the formula, X1 and X2 are, respectively, an atomic group linkable to the end of P₁ in Structural Formula (1), and A is an atomic group linkable to X1 and X2.

[32] The present invention is also related to the method for treating the polymer in Item [27], wherein the method further comprises a step of depolymerizing the polymer represented by the above Structural Formula (1) by addition of a compound having a condensable functional group and a spin-trapping group, and a step of condensing the substance obtained by the above depolymerization step to re-obtain a polymer.

[33] The present invention is also related to the method for treating the polymer in Item [32], wherein the polymer represented by the above Structural Formula (1) is any of the polymers in Items [2] to [16], [11′], and [11″].

[34] The present invention is also related to the method for treating the polymer in Item [32], wherein the compound having a condensable functional group and a spin-trapping group is represented by Structural Formula (3) below: X₃—M₁—X₄  (3). In the formula, X₃ is a condensable functional group; X₄ is a spin-trapping group; and M₁ is selected from the group consisting of —(CH₂)_(n2)—, —C₆H₄— and —(CH₂)_(m1)—C₆H₄—(CH₂)_(m2)— (n2, m1, and m2 are, respectively, an integer from 1 to 8).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows molecular weight distribution (differential curve) by GPC of the polymer obtained in Example 10.

FIG. 2 shows the results of the FT-IR measurement of the polymer obtained in Example 10.

FIG. 3 shows the results of a measurement of thermal decomposition characteristics of the polymer obtained in Example 10.

FIG. 4 shows molecular weight distribution (differential curve) by GPC of the polystyrene polymer decomposed and recovered in Example 35.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below in detail.

(Polymer)

The essential compound in the present invention is the polymer represented by Structural Formula (1): [—P₁—R—]_(n)  (1). In the formula, P₁ indicates an addition polymer moiety having a continuous hydrocarbon skeleton, namely a moiety of a polymer or oligomer formed by addition polymerization of one or more kinds of double bond-containing monomers; R indicates a linking moiety constituted of a condensation system for linking plural P₁ moieties; and n is a number of the repeating units and an integer of 2 or more. For selective depolymerization at the portion R, the P₁ moiety should not contain a condensation system, such as ester linkage (mentioned below). The linking moieties R are classified roughly into two types. The types of the polymer depending on the linking moiety are explained according to the linking mode. Linking Mode 1

In a first preferred mode, the addition polymer moieties P₁ are linked directly by a dissociable linkage without a spacer. The example include linkage of the polymer moieties P₁ by ester linkage (—COO—), amide linkage (—CONH—), urethane linkage (—NH—COO—), urea linkage (—NH—CO—NH—), and the like. In such a mode of linkage, the orientation direction of the linkage in the main chain may be the same along the main chain throughout the repeating units, or may be reversed alternately between the adjacent repeating units. For example, [1] in a first case, the polymer P₁ has a carboxyl group introduced to one end and an amino group introduced to the other end (the linkage direction in the main chain is the same throughout the repeating units), and [2] in a second case, a polymer P₁ having a carboxyl group at the respective ends and another kind of the polymer having an amino group at the respective ends are linked together (the direction of the linkage is reversed alternately between the adjacent repeating units).

Linking Mode 2

In a second preferred mode, the linking moiety R is derived from a lower molecular compound represented by Structural Formula (2): X1-A—X2  (2). In the formula, X1 and X2 are, respectively, an atomic group capable of linking to the end of the addition polymer P₁, and A is a spacer mentioned below.

The groups X1 and X2 are dissociable, and preferably are any one selected respectively from ester linkage (—COO—), amide linkage (—CONH—), urethane linkage (—NH—COO—), urea linkage (—NH—CO—NH—). Of these, the amide linkage is particularly preferred. In this linking mode, X1 and X2 may be identical, or X1 and X2 may be different from each other. The combination of X1 and X2 is selected depending on the availability and convenience in the depolymerization mentioned below.

In the case where X1 and X2 are different from each other, the arrangement of X1 and X2 may be the same throughout the repeating units, or may be reversed alternately between the adjacent repeating units. For example, condensation of the polymer P₁ having a carboxyl group on respective ends with ethanolamine, two types of linkages are possible: [1] one end of P₁ is an amide and the other end thereof is ester, and [2] both ends of P₁ are amides or esters. The type of the linkage is selected in view of the reaction efficiency in the synthesis and the convenience in depolymerization mentioned below.

In the case where X1 and X2 are identical, X1 and X2 are dissociable (reversibly reactive). In this case, the orientation direction of the linkage may be the same throughout the repeating units, or reversed alternately between the adjacent repeating units. The type of the linkage is selected in consideration of the availability of the source materials and the convenience in the depolymerization mentioned below. For example, in the case where a polymer P₁ having a carboxyl group, respectively, at the both ends is condensed with ethanol amine, [1] P₁ may have an amide linkage on one end and an ester linkage at the other end, or [2] P₁ may have an amide linkage at the respective ends or an ester linkage at the respective ends of P. The types of the linkage are selected in consideration of reaction efficiency in the synthesis and the convenience in depolymerization mentioned below.

Composition of Respective Constituting Components

Specifically, the addition polymer moiety P₁ includes polymer moieties constituted of polystyrene, polybutadiene, polyacrylonitrile, polyethylene and polypropylene, and copolymers thereof. The addition polymer moiety P₁ should not contain a condensation system, such as esters and amides. The polymerization degree of the polymer moiety is selected in view of the molecular weight of the entire polymer and the content of the dissociable linkage, the mechanical strength and other properties, and the ease of depolymerization. Accordingly, the range thereof cannot be decided definitely, but is preferably 2, or more, more preferably in the range from 2 to 2000, in view of the synthesis process.

The spacer A in the above Linking Mode 2 includes, preferably, those, which do not impair the properties of the polymer P₁. The spacer A may be an aliphatic group, such as an alkylene of 1-14 carbons, or an aromatic group, but is preferably a group containing at least an aromatic moiety in view of the water-resistance and the polymerization reactivity. In particular, for the block having an aromatic ring like polystyrene, preferred are an alkylene having a phenyl in the side chain (e.g., —CHPh—CH₂—), an alkylene having a phenylene in the main chain (e.g., —CH₂—Ph—CH₂—), and a phenylene (—Ph—).

On the other hand, the linkage moiety having the spacer A includes compounds having at least one aromatic moiety, such as p-phenylenediamine, m-phenylenediamine, p-xylenediamine, m-xylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 2-(4-aminophenyl)ethylamine, and 2,2′-dithiodianiline.

The spacer A also includes moieties of aliphatic compounds, such as 3,3′-diaminopropylamine, and 2,2′-diaminodiethyl ether.

Production Process

The polymer of the present invention is synthesized by condensing a compound having a functional group on the respective both ends singly or with a bifunctional compound. Specifically, in Linking Mode 1, an addition polymer P having a functional group, such as an amino group and a carboxyl group, at the respective both ends, and the functionalized polymer are condensed in a molten state or in a solution, and if necessary, by using a catalyst or an active intermediate. In Linking Mode 2, similarly, the compound P₁ functionalized at the both ends and a bifunctional compound (a source material giving the moiety represented by Structural Formula (2)) are condensed. The molecular weight of the final polymer is preferably in the range of 10⁴ to 10⁶.

Molded Article

The polymer of the present invention can be molded into molded resin articles similar to the high polymer of the constituting addition polymer component. That is, the resin produced from the thermoplastic polymer P₁ component can be molded by a conventional molding process, such as compression molding, extrusion molding, and injection molding, whereby a novel recyclable molded resin article can be provided, as described below. The molded article may contain a plasticizer, a colorant, a filler, a stabilizer, and a flame retardant, provided that the recycling is not prevented.

Depolymerization and Recycling

The polymer of the present invention can be depolymerized by cutting selectively the dissociable linkage in the coupling moiety to obtain a re-condensable parts. The depolymerization can be conducted with a relatively small energy input, since the depolymerization is conducted by cutting the dissociable linkage. The reaction utilized for the depolymerization is not specially limited. A hydrolysis reaction can be readily used. For example, a molded article itself, after use, or a flaked article thereof, is subjected to hydrolysis with an acid or alkali catalyst under mild conditions to depolymerize the linkage. The depolymerization facilitates removal of deteriorated portions and removal of an additive, enabling recovery of the recycling source material in a more refined state.

In Linking Mode 2, two cutting methods are applicable: in one method, both X1 and X2 in the coupling moiety R are cut; and in the other method, only one of the two is cut. In the latter method, the linking groups X1 and X2 are preferably different from each other. The selective cutting of one of the linking groups is advantageous in the case where the orientation of X1 and X2 is the same throughout the repeating units, since the depolymerization gives the repeating units as a simple product, thereby facilitating treatment for the purification and recondensation.

The depolymerization product is regenerated by recondensation without a preliminary treatment or is modified for reactivity, if necessary, into the original polymer (1). The polymer can be formed into molded articles. Also, if necessary, the condensation degree (n in Structural Formula (1)) may be changed, or the linking mode may be changed to control the physical properties.

Addition of Spin-Trapping Compound

To attain the object of the present under severe conditions, such that the cutting occurs within the addition polymer moiety P₁, Compound (B) is preferably added, which compound has a spin-trapping function. By reacting Polymer (A) and Compound (B), a condensing functional group is introduced to the molecular end of Polymer (A).

The addition of Compound (B) having a spin-trapping function is known. For example, Japanese Patent Application Laid-Open No. 9-176372 discloses addition of an isoxazolidinone compound for the purpose of stabilizing the melt flow and preventing discoloration; and Japanese Patent Application Laid-Open No. 7-324028 discloses addition of a spin-trapping compound to a cosmetic or dermatologic composition for the purpose of light protection, aging prevention, and/or acne treatment. These methods are intended to prevent oxidation deterioration of matrix materials by trapping peroxide radicals formed by oxygen or oxidation using the spin-trapping compound. The intention of the methods in the above disclosures is to prevent deterioration of a material, and not to restore polymer molecules. These methods are not effective for such a purpose.

On the other hand, the mechanism in the present invention is as described below. When a polymer is cut by external stress, free radicals are formed at the cut site. A compound (B) having a condensable functional group and a spin-trapping group, if coexists, traps free radicals, and consequently, the condensable functional group of Compound (B) is introduced to the cut end of the polymer.

Compound (B) having a condensable functional group and a spin-trapping group is represented by Structural Formula (3): X₃—M₁—X₄  (3), where X₃ is a condensable functional group, X₄ is a spin-trapping group, and M₁ is the groups represented by Structural Formula (4):

where n2, m1 and m2 are, respectively, an integer of 1 to 8, and the linking site on the aromatic ring may be an ortho position or a meta position, different from the para position shown in the formulas.

The condensable functional group X₃ is a usual condensable functional group, such as carboxyl, hydroxyl, and amino. The spin-trapping group X₄ is preferably a nitroso-containing group. The nitroso group-containing compound is exemplified by the compound represented by Structural Formula (5):

Otherwise, paranitrosodurene derivatives are also useful.

The restoration of a molecule by the above reaction is useful, for example, in the process below. Firstly, in a system in which the addition polymer having a condensable functional group at the respective ends of the molecule is used for repeated polymerization-depolymerization, especially, in the depolymerization step, the molecule can be cut by agitation or the like. In this step, the compound having a condensable functional group and a spin-trapping group, if present, will trap the radical formed by the cutting by the spin-trapping group. In this process, if oxygen present in the polymer solution when the molecule is cut, the reactive oxygen reacts selectively with the radical formed by cutting to form an unwanted peroxide radical. Therefore, the oxygen should be removed completely from the solution by bubbling an inert gas like nitrogen into the solution, and the reaction itself should be conducted in an inert gas atmosphere.

Next, in a process in which the high polymer obtained by the polymerization is molded, a compound having a condensable functional group and a spin-trapping group is preferably mixed into the polymer preliminarily. In the molding machine, heat and a shearing stress applied to the resin cause scission of the molecular chain, but the radical formed by molecular scission is trapped even in the solid phase by the spin-trapping group.

The concentration of the compound having the condensable functional group and the spin-trapping group to be mixed ranges, in the former case of the solution reaction, preferably from 0.01% to 5%, more preferably from 0.1% to 3%, based on the source resin, and in the latter case of the solid operation, ranges preferably from 0.1% to 5%, since the movement of the molecule is restricted in the solid phase in comparison with the reaction in the solution.

As described above, in the technique of polymerization-depolymerization using a polymer having two functional groups and a coupling compound capable of linking to the two functional group, the addition of a compound having a condensable functional group and a spin-trapping group can improve the reproducibility of the repetition and reliability of the reaction, such as the yield, purity, and properties of the resin. With this technique, the regeneration cycles can be increased significantly. That is, the resin used as molded articles or packaging materials can be recovered and depolymerized for reuse as the source material of the resin. Thus, the usefulness of the regenerated resin produced by the repolymerization is not reduced. Such a technique will change greatly conventional recycle techniques, which are limited in application.

Moreover, the technique of the present invention can be combined with various conventional techniques, such as the reuse techniques for molded articles, material recycling techniques for sandwich molding, chemical recycling techniques of decomposition of a resin to the source monomer, and thermal recycling technique of utilizing heat of combustion, and so forth, without limiting the material recycling model.

EXAMPLES

The present invention is further described below specifically without limiting the present invention.

Example 1 Synthesis of Ester-Linked Polymer Having Spacer, 1

2 g of 1,4-butanediol and 5 g of a polystyrene having a carboxylic acid group at the respective ends (Mw: 25,000, produced by Scientific Polymer Product Co.; Mw indicates a weight-average molecular weight) were placed in a flask. The mixture was heated to 180° C. in a nitrogen atmosphere. Thereto was added 35 mg of tetraisopropyl orthotitanate diluted with 100 μL of toluene, and the mixture was stirred. Then, the mixture was kept at a temperature of 180-200° C. to remove the water formed and the diol by distillation. The reaction was continued under a reduced pressure to the final pressure of 6.67 kPa. The reaction product was taken out from the flask in a hot state to obtain a polymer in a white wax state (Compound No. A-1).

The molecular weight was measure by gel permeation chromatography (herein after referred to as “GPC”) under the measurement conditions shown below.

Measurement apparatus: HLC 8120 GPC (Tosoh Corp.)

Columns: TSKgel SuperHZM-M+HZM-N

Elution Liquid: THF, 40□

Standard: Polystyrene (Polymer Laboratories Co.)

The weight-average molecular weight of the resulting polymer was 400,000, and therefore, the number (n) of the repeating units is estimated to be about 16.

Examples 2 to 5 Syntheses of Ester-Linked Polymer Having Spacer, 2 to 5

The synthesis was conducted under the same conditions as in Example 1, except that the polymer moiety (P) of the polystyrene (PS) having a carboxyl group at the respective ends was replaced by a moiety of polystyrene of a different molecular weight, polypropylene, or polyethylene (PE); and 1,4-butanediol was replaced by another diol.

Table 1 below shows Examples 1 to 5.

For simplicity of representation, Synthesis Example 1 is summarized as A-1 in the table, in which the ester-linked polymer of the number of repeating units (n) of 16 was prepared from 1,4-butanediol and the polystyrene having a carboxylic acid group at both ends (Mw: 25,000, Mw representing weight-average molecular weight). Examples 2 to 5 are summarized in the same style.

TABLE 1 Example Compd R No. No. P (Mw) X1 A X2 n 1 A-1 PS COO 1,4-C₄H₈ OCO 16 (25,000) 2 A-2 PS(15,000) COO

OCO 4 3 A-3 PP COO 1,8-C₈H₁₆ OCO 70 (5,000) 4 A-4 PE COO 2,5-C₆H₁₂ OCO 9 (50,000) 5 A-5 PS(100,000) COO

OCO 3

Example 6 Synthesis of Amide-Linked Polymer Having Spacer

A 5-gram portion of polystyrene dicarboxylic acid having a carboxyl group at the respective ends (Mw: 15,000) was suspended in 100 mL of ethanol. To this suspension, was added a solution of 0.2 g of hexane-1,6-diamine in 10 mL ethanol. The mixture was stirred at room temperature. Thereby, a white precipitate was formed with heat generation. After completion of the reaction, the crystalline matter was collected by filtration and washed with ethanol twice to obtain a nylon salt. A 3-gram portion of this nylon salt was placed in a flask, and after purging with nitrogen, the salt was heated with gradual evacuation to melt the salt. The content in the flask became viscous gradually to form a pale yellow opaque polymer (Compound No. B-1).

The resulting polymer had a weight-average molecular weight of 465,000 according to a GPC measurement, and the number of the repeating units (n) was estimated to be about 31.

Examples 7 to 9 Synthesis of Amide-Linked Polymer Having Spacer, 2 to 4

Polymers were prepared under the same conditions and in the same manner as in Example 6, except that the polymer moiety (P) of the polystyrene (PS) having the carboxyl groups at the respective ends was changed to polystyrene of a different molecular weight or polypropylene (PP), and the hexane-1,6-diamine was changed to another diol compound.

Table 2 below shows Examples 6 to 9.

For simplicity of representation, Synthesis Example 6, in which the amide-linked polymer of the number of repeating units (n) of 31 was prepared from hexane-1,6-diamine and the polystyrene having a carboxyl group at the respective ends (Mw: 15,000, Mw representing weight-average molecular weight), is summarized as B-1 in the table. Examples 7 to 9 are summarized in the same style.

TABLE 2 Example Compd R No. No. P (Mw) X1 A X2 n 6 B-1 PS CONH 1,6-C₆H₁₂ NHCO 31 (15,000) 7 B-2 PS CONH 1,3-C₆H₆ NHCO 7 (100,000) 8 B-3 PP CONH 2,5-C₅H₁₀ NHCO 24 (50,000) 9 B-4 PE(2,000) CONH

NHCO 10

Example 10 Synthesis of Amide-Linked Polymer Having Spacer, 5

5.0 g (0.2 mmol) of PS dicarboxylic acid having Mw of 25,000; 40.05 mg (0.2 mmol) of 4,4′-diaminophenyl ether; 248 mg (0.8 mmol) of triphenyl phosphite; and 30 mg of lithium chloride were placed in a flask equipped with a nitrogen-introducing tube and a stirrer. The mixture in the flask was dissolved in 2 mL of N-methylpyrrolidone (NMP) and 0.2 mL of pyridine. The solution was stirred at 100° C. for one hour in a nitrogen atmosphere. The resulting polymer solution was poured into 200 mL of methanol, and the deposited polymer was collected by filtration. The collected polymer was refluxed in 100 mL of methanol for one hour to remove the remaining solvent and condensing agent. Then, the polymer was collected by filtration and was dried in vacuo to obtain a white fibrous polymer (Compound No. B-5).

The molecular weight was measured by GPC under the measurement conditions shown below.

Measurement apparatus: HLC 8120 GPC (Tosoh Corp.)

Columns: TSKgel SuperHZM-M+HZM-N

Elution Liquid: THF, 40□

Standard: Polystyrene (Polymer Laboratories Co.)

The weight-average molecular weight of the resulting polymer was 370,000, and the number (n) of the repeating units is estimated to be about 11. FIG. 1 shows the molecular weight distribution (differential curve) as measured by GPC. In FIG. 1, curve 1 corresponds to the source PS, curve 2 corresponds to the intermediate state during the polymerization, and curve 3 corresponds to the final polymer.

FIG. 2 shows FT-IR measurement results of the obtained polymer. The measurement was conducted by a KBr tablet method by means of the apparatus 1720× (Perkin Elmer Co.).

The absorption peaks a of Amide I are found at 1687 cm⁻¹ and 1653 cm⁻¹. The absorption peak a of Amide II is found at 1560 cm¹. The absorption peaks b of the aromatic ether are found at 1262 cm⁻¹ and 1217 cm⁻¹. Thereby, it was confirmed that the polymer had been formed by the amide linkage.

Thermal decomposition characteristics were measured by thermogravimetry (TG) by TG-DTA 2000 S (MacScience Co.) in the temperature range up to 500° C. at a temperature elevation rate of 10° C./min in N₂ gas. FIG. 3 shows the measurement results. In FIG. 3, curve A corresponds to the polymer obtained in this Example, and curve B corresponds to the commercial PS.

FIG. 3 shows that the polymer of this Example has the same thermal decomposition characteristics with the same thermal decomposition initiation temperature and the same heat resistance as the PS (PS Wako Junyaku K.K.) having no amide linkage.

Example 11 Synthesis of Amide-Linked Polymer Having Spacer, 6

10.0 g (0.4 mmol) of PS dicarboxylic acid having Mw of 50,000; 80.25 mg (0.4 mmol) of 4,4′-diaminophenylmethane; 490 mg (0.8 mmol) of triphenyl phosphite; and 60 mg of calcium chloride were placed in a flask equipped with a nitrogen-introducing tube and a stirrer. The mixture in the flask was dissolved in 4 mL of NMP and 0.4 mL of pyridine. The solution was stirred at 100° C. for two hours in a nitrogen atmosphere. The resulting polymer solution was poured into 400 mL of methanol, and the deposited polymer was collected by filtration. The collected polymer was refluxed in 200 mL of methanol for one hour. Then, the polymer was collected by filtration and was dried in vacuo to obtain a white fibrous polymer (Compound No. B-6). The weight-average molecular weight of the polymer was 520,000 according to the GPC measurement.

Example 12 Synthesis of Amide-Linked Polymer Having Spacer, 7

12.5 g (0.25 mmol) of polyethylene-dicarboxylic acid having Mw of 4,000; 54.1 mg (0.5 mmol) of p-phenylenediamine; 310 mg (1 mmol) of triphenyl phosphite; 100 mg of lithium chloride; and 300 mg of calcium chloride were placed in a flask equipped with a nitrogen-introducing tube and a stirrer. The mixture in the flask was dissolved in 5 mL of NMP and 1 mL of pyridine. The solution was stirred at 100° C. for 6 hours in a nitrogen atmosphere. The polymer solution was poured into 300 mL of methanol, and the deposited polymer was collected by filtration. The collected polymer was refluxed in 150 mL of methanol for one hour. Then, the polymer was collected by filtration and was dried in vacuo to obtain a white fibrous polymer (Compound No. B-7). The weight-average molecular weight of the polymer was 120,000 according to the GPC measurement.

Example 13 Synthesis of Amide-Linked Polymer Having Spacer, 8

10.0 g of polypropylene-dicarboxylic acid having Mw of 5,000; 80 mg of p-xylenediamine; and 500 mg of triphenyl phosphite were placed in a flask equipped with a nitrogen-introducing tube and a stirrer. The mixture in the flask was dissolved in 4 mL of NMP and 1 mL of pyridine. The solution was stirred at 100° C. for 5 hours in a nitrogen atmosphere. The resulting polymer solution was poured into 400 mL of methanol, and the deposited polymer was collected by filtration. The collected polymer was refluxed in 200 mL of methanol for one hour. Then, the polymer was collected by filtration and was dried in vacuo to obtain a white fibrous polymer (Compound No. B-8). The weight-average molecular weight of the polymer was 90,000 according to the GPC measurement.

Example 14 Synthesis of Amide-Linked Polymer Having Spacer, 9

10.0 g of α-amino-ω-carboxy-terminated-polyethylene (Mw 4,000); 500 mg (0.8 mmol) of triphenyl phosphite; and 60 mg of lithium chloride were placed in a flask equipped with a nitrogen-introducing tube and a stirrer. The mixture in the flask was dissolved in 5 mL of pyridine. The solution was stirred at 100° C. for 5 hours in a nitrogen atmosphere. The resulting polymer solution was poured into 400 mL of methanol, and the deposited polymer was collected by filtration. The collected polymer was refluxed in 200 mL of methanol for one hour. Then, the polymer was collected by filtration and was dried in vacuo to obtain a white fibrous polymer (Compound No. B-9). The weight-average molecular weight of the polymer was 20,000 according to the GPC measurement.

Example 15 Synthesis of Ester-Linked Polymer Having No Spacer, 1

A 3-gram portion of α-hydroxy-ω-carboxy-terminated-polystyrene (Mw: 50,000, Polymer Science Co.) was placed in a flask and heated to 180° C. in a nitrogen atmosphere. Thereto, 35 mg of dibutyltin oxide was added and stirred. The formed water and diol were removed by distillation at the temperature kept at 180-200° C. The reaction was continued at a reduced pressure. Then, the reaction product was taken out from the flask while it was hot to obtain white polymer (Compound C-1). The weight-average molecular weight of the obtained polymer was 700,000 according to the GPC measurement. The number of the repeating units was estimated to be about 14.

Examples 16 and 17 Synthesis of Ester-Linked Polymers Having No Spacer, 2-3

Ester-linked polymers of Examples 16 and 17 were synthesized under the same conditions as in Example 15, except that the α-hydroxy-ω-carboxy-terminated polystyrene was changed to a polystyrene having different molecular weight or to a polyethylene.

Examples 18 and 19 Synthesis of Amide-Linked Polymers Having No Spacer, 1 and 2

Amide-linked polymers of Examples 18 and 19 were synthesized under the same conditions as in Example 15, except that the α-hydroxy-ω-carboxy-terminated-polystyrene was changed into α-amino-ω-carboxy-terminated-polystyrene or -polypropylene.

Table 3 shows the results of Examples 15 to 19.

For simplicity of representation, Synthesis Example is summarized as C-1 in the table, in which the linked polymer of the number of repeating units (n) of 14 was prepared from α-hydroxy-ω-carboxy-terminated-polystyrene (Mw: 50,000, Mw representing weight-average molecular weight). Examples 16 to 19 are summarized in the same style. Incidentally, in the case where α-amino-(ω-carboxy-terminated-polystyrene was used, R is represented by CONH.

TABLE 3 Example Compound No. No. P R n 15 C-1 PS (50,000) COO 14 16 C-2 PS (5000) COO 8 17 C-3 PE (20,000) COO 27 18 D-1 PP (4000) CONH 4 19 D-2 PS (10,000) CONH 21

Example 20

(Synthesis of Amide-Linked Polymers Having No Spacer, 3)

A 3-gram portion of α-amino-ω-carboxy-terminated-polystyrene (Mw 50,000) was placed in a flask, and was heated to 180□ in a nitrogen atmosphere. Thereto, 35 mg of dibutyltin oxide was added and stirred. The formed water and diol were removed by distillation at the temperature kept at 180-200° C. The reaction was continued at a reduced pressure. Then, the reaction product was taken out from the flask while it was hot to obtain white polymer (Compound D-3).

The weight-average molecular weight of the obtained polymer was 500,000 according to the GPC measurement.

Example 21 Synthesis of Urethane-Linked Polymer Having Spacer, 1

Distilled chlorobenzene and o-dichlorobenzene were mixed at a mixing ratio of 80/20 (vol/vol). This mixed solvent was used as the reaction solvent. A 3-gram portion of 1,4-butanediol and 120 mL of the solvent were placed in a four-neck flask equipped with a stirrer, a thermometer, a nitrogen-introducing tube, and a reflux condenser with a drying tube attached. The flask was purged sufficiently with nitrogen, and then the nitrogen-introducing tube was changed to a dropping funnel with a drying tube attached thereto. 5 g of polystyrene having a terminal isocyanate group at the respective ends and 60 mL of the solvent were placed in the dropping funnel. The flask was heated with stirring. With the start of stirring, half of the content in the dropping funnel was added in one lot to the flask with vigorous stirring. The remaining half of the dropping funnel content was added dropwise in 3 hours, and thereafter, the reaction mixture was refluxed for one hour. After cooling to room temperature, the deposited polymer was collected by filtration. The polymer was dissolved in hot dimethylformamide. Thereto, 50 mL of methanol was added, and the mixture was left standing in a refrigerator overnight. The reprecipitated polymer was collected by filtration and vacuum-dried (Compound No. E-1).

The weight-average molecular weight of the resulting polymer was 300,000, and the polymerization degree was estimated to be about 30.

Examples 22 to 25 Synthesis of Urethane-Linked Polymers Having Spacer, 2 to 5

The synthesis was conducted in the same manner as in Example 21, except that the polymer moiety (P) of the polystyrene (PS) having terminal isocyanate groups at the respective ends was changed to a polystyrene of a different molecular weight, polypropylene (PP), or polyethylene (PE), and the 1,4-butanediol was changed to another diol compound.

Table 4 shows Examples 21 to 25.

For simplicity of representation, Synthesis Example of Example 21 is summarized as E-1 in the table, in which the linked polymer of the number of repeating units (n) of 30 was prepared from 1,4-butanediol and polystyrene having a terminal isocyanate group at the respective ends (Mw: 10,000, Mw representing weight-average molecular weight). Examples 22-25 are summarized in the same style.

TABLE 4 Example Compd R No. No. P X1 A X2 n 21 E-1 PS OCONH 1,4-C₄H₈ NHOCO 30 (10,000) 22 E-2 PS OCONH 1,12-C₁₂H₂₄ NHOCO 22 (5,000) 23 E-3 PP OCONH C₂H₄ NHOCO (50,000) 24 E-4 PE(10,000) OCONH

NHOCO 6 25 E-5 PS OCONH 1,8-C₉H₁₈ NHOCO 12 (25,000)

Example 26 Synthesis of Urea-Linked Polymer Having Spacer, 1

Chlorobenzene and o-dichlorobenzene both having been distilled were mixed at a mixing ratio of 80/20 (vol/vol). This mixed solvent was used as the reaction solvent. A 3-gram portion of hexane-1,6-diamine and 120 mL of the solvent were placed in a four-neck flask equipped with a stirrer, a thermometer, a nitrogen-introducing tube, and a reflux condenser with a drying tube attached. The flask was purged sufficiently with nitrogen, and then the nitrogen-introducing tube was changed to a dropping funnel with a drying tube attached thereto. 5 g of polystyrene having an isocyanate group at the respective ends (Mw 5000) and 60 mL of the solvent were placed in the dropping funnel. The flask was heated with stirring. With the start of the stirring, half of the content in the dropping funnel was added in one lot to the flask with vigorous stirring. The remaining half of the dropping funnel content was added dropwise in 3 hours, and thereafter, the reaction mixture was refluxed for one hour. After cooling to room temperature, the deposited polymer was collected by filtration. The polymer was dissolved in hot dimethylformamide. Thereto, 50 mL of methanol was added, and the mixture was left standing in a refrigerator overnight. The reprecipitated polymer was collected by filtration and vacuum-dried (Compound No. F-1)

The weight-average molecular weight of the resulting polymer was 100,000 according to the GPC measurement, and the number of the repeating units (n) was estimated to be about 20.

Table 5 shows Example 26.

For simplicity of representation, Synthesis Example of Example 26 is summarized as F-1 in the table in which the urea-linked polymer of the number of repeating units (n) of 20 was prepared from hexane-1,6-diamine and polystyrene having an isocyanate group at the respective ends (Mw: 5,000, Mw representing weight-average molecular weight).

TABLE 5 Example Compd R No. No. P ×1 A ×2 n 26 F-1 PS NHCONH 1,6-C₆H₁₂ NHCONH 20 (5,000)

Examples 27 to 33 Molding

The powdery polymers synthesized in the above Examples were molded by the methods shown in Table 6. As a result, satisfactory molded articles were obtained.

TABLE 6 Exam- ple Poly- No. mer Method Conditions Shape 27 B-4 Compres- 200□, 3 MPa Square plate sion 20 cm × 20 cm × 3 mm 28 D-4 Compres- 200□, 3 MPa Square plate sion 20 cm × 20 cm × 3 mm 29 C-1 Extrusion 220□, 100 rpm Round bar Single screw 5 mm φ 30 A-1 Injection 220□ (Tip) Cup Inj. pressure 5 cm φ × 7 cm 90 MPa 1 mm thick 31 B-5 Compres- 200□, 3 MPa Square plate sion 20 cm × 20 cm × 3 mm 32 B-9 Extrusion 210□, 100 rpm Round bar 5 mm φ Single screw 33 B-6 Injection 220□ (Tip) Cup Inj. pressure 5 cm φ × 7 cm 80 MPa 1 mm thick

Example 34 Recycling

The molded article formed in Example 30 was crushed. A 10-gram portion of the crushed matter was dissolved in 400 mL of toluene. Thereto, 400 mL of aqueous 1-mol/L (1N) sodium hydroxide solution was added. The mixture was stirred at 100° C. for 24 hours. The molecular weight of the polymer was confirmed by GPC to have decreased to the value of the starting polystyrene polymer. After removal of the solvent by distillation, the recovered matter washed with aqueous 10% acetic acid solution, further washed with ethanol, and dried. The recovered matter was confirmed to be a polystyrene derivative by infrared spectrometry. The recovered powdery matter was treated for the synthesis in the same manner as in Example 1. Thereby, the same results were obtained.

Example 35 Recycling

The molded article formed in Example 31 was crushed. A 10-gram portion of the crushed matter was dissolved in 300 mL of xylene. Thereto, 100 mL of 94% sulfuric acid was added, and the mixture was stirred at 110° C. for 27 hours. FIG. 4 shows the differential curves of the molecular weight distribution. In FIG. 4, curve 4 corresponds to the molded polymer article, curve 5 corresponds to a treated polymer after 7 hours from starting the treatment, and curve 6 corresponds to the recycled matter. As shown in FIG. 4, it was confirmed by GPC that the molecular weight of the polymer decreased to the value of the starting styrene polymer. After removal of the solvent by distillation, the recovered matter was washed with aqueous 1-mol/L (1N) sodium hydrogencarbonate solution, further washed with ethanol, and dried. The recovered matter was confirmed by infrared spectrometry to be a polystyrene derivative. The recovered powdery matter was used for the synthesis in the same manner as in Example 10, whereby the same results were obtained.

Example 36 Synthesis of Polymer, 1

A styrene polymer having a carboxyl group at the respective ends and having a molecular weight of 25,000 is employed as the polymer having two condensable functional groups. Butanediol is employed which has two functional groups linkable to the two carboxyl groups, as the coupler for the aforementioned polymer. These compounds are heated to 180° C. in a flask. Thereto, titanium isopropoxide is added in an amount of 0.5 mass % as the catalyst with stirring. The reaction flask is purged by gaseous nitrogen and evacuated gradually to 6.67 kPa to remove the water formed by the dehydration condensation. After 3 hours of reaction, the polymer is recovered.

Decomposition of Polymer, 1

The synthesized polymer is dissolved N,N′-dimethylformamide (DMF) at a concentration of 10 mass %. Thereto, 1 mol/L (1N) hydrochloric acid is added and the mixture is stirred at 40° C. for 5 hours to hydrolyze the polymer. In the hydrolysis, the compound represented by Structural Formula (6) below is added thereto in an amount of 0.1% as the compound having a condensable functional group and a spin-trapping group:

The resulting styrene polymer having a carboxyl group at the respective ends of the molecule and having a molecular weight of 25,000 is recovered by repetition of dissolution in toluene and precipitation by methanol. The butanediol formed by the decomposition is recovered by distillation.

Resynthesis of Polymer, 1

A polymer is synthesized by using, as the starting materials, the recovered styrene polymer having a carboxyl group at the respective ends and having a molecular weight of 25,000 and butanediol, in the same manner as in “Synthesis of Polymer, 1” described above.

The polymer obtained in “Synthesis of Polymer, 1” and the polymer obtained in “Resynthesis of Polymer, 1” are confirmed to be equivalent by molecular weight distribution measurement by GPC.

Example 37

Molding of Polymer, 1

The polymer having been synthesized in Example 36 “Synthesis of Polymer, 1” is used as a molding material for molding with addition of the compound represented by Structural Formula (7) as the compound having a condensable functional group and a spin-trapping group in an amount of 1%:

This molding material is extrusion-molded at 180° C. into a printer case.

Decomposition of Polymer, 2

The molded polymer is hydrolyzed in the same manner as in “Decomposition of Polymer, 1” in Example 1. In the hydrolysis of this Example, the compound of Structural Formula (7) having a condensable group and a spin-trapping group need not necessarily be newly added since the compound has been already added.

Resynthesis of Polymer, 2

A polymer is produced from the recovered material in the same manner as in “Resynthesis of Polymer, 1”. The molecular weight distribution of the resynthesized polymer and that of the polymer before the molding operation are confirmed to be equivalent by GPC.

Example 38

Synthesis of Polymer, 2

Two styrene polymers are employed: one having a carboxyl group at the respective ends of the molecule and having a molecular weight of 25,000 and another having a hydroxyl group at the respective ends of the molecule, as the polymers having two condensable functional groups. These compounds are heated together to 180° C. in a flask. Thereto, titanium isopropoxide is added in an amount of 0.5 mass % as the catalyst. The reaction flask is purged by gaseous nitrogen and evacuated gradually to 6.67 kPa to remove the water formed by the dehydration condensation. After 5 hours of the reaction, the polymer is recovered.

Decomposition of Polymer, 3

The synthesized polymer in “Synthesis of Polymer, 2” is dissolved N,N′-dimethylformamide (DMF) at a concentration of 10 mass %. Thereto, 1-mol/L (1N) hydrochloric acid is added, and the mixture is stirred at 40° C. for 5 hours to hydrolyze the polymer. In the hydrolysis, a compound represented by Structural Formula (6) described in Example 36 is added in an amount of 0.1% based on the polymer as the compound having a condensable functional group and a spin-trapping group.

The resulting styrene polymers, one having a carboxyl group at the respective ends of the molecule and having a molecular weight of 25,000 and the other having a hydroxyl group at the respective ends of the molecule and having a molecular weight of 25,000, are recovered by repetition of dissolution in toluene and precipitation by methanol.

Resynthesis of Polymer, 3

A polymer is synthesized by dehydration condensing the styrene polymer having a carboxyl group at the respective ends of the molecule and having a molecular weight of 25,000 and the one having a hydroxyl group at the respective ends of the molecule and having a molecular weight of 25,000, which have been recovered in the above “Decomposition of Polymer, 3”, in the same manner as in “Synthesis of Polymer, 2” described above.

The polymer has the molecular weight and molecular weight distribution equivalent to the polymer obtained in “Synthesis of Polymer, 2”.

Example 39

Recycling Method

The polymer obtained in Example 36 is molded in the same manner as “Molding of Polymer, 1” in Example 37 into a printer case. The molded products after use are collected from users. Some of the collected cases are decomposed by the method of “Decomposition of Polymer, 1” of Example 36 to obtain a new source material for polymer synthesis. From this material, a polymer is synthesized anew by the method of “Resynthesis of Polymer, 1” of Example 36. Separately, the rest of the collected cases are chipped without a preliminary treatment and transformed by sandwich-molding into printer cases by the method described in Japanese Patent Publication No. 6-24739 (Patent Literature 1).

These recycling steps may be conducted by the same company or may be shared by more than one company.

Reference Example 1

Decomposition of Polymer 4

The polymer obtained in Example 36 is hydrolyzed in the same manner as in “Decomposition of Polymer 1” in Example 36, except that the compound of Structural Formula (6) is not added. Thereby, the styrene polymer having a carboxyl group at the respective ends and butanediol are recovered.

Resynthesis of Polymer, 4

From the recovered styrene polymer having a carboxyl group at the respective ends and butanediol, a polymer is synthesized in the same manner as in “Resynthesis of Polymer, 1” in Example 36.

The polymer obtained in “Synthesis of Polymer, 1” in Example 36 and the polymer obtained this “Resynthesis of Polymer, 4” are subjected to the GPC measurement to compare the molecular weight distribution. As a result, the polymer obtained in “Resynthesis of Polymer, 4” has a lower molecular weight.

The present invention provides a novel polymeric material that is reversibly synthesizable and decomposable. Further, the decomposition-resynthesis technique of the present invention enables a novel material-recycling system with less energy input. Furthermore, the present invention, by being combined with any of reuse technique, material-recycling technique, chemical recycling technique, thermal recycling technique and so forth, enables a remarkably effective use of source materials in comparison with conventional techniques, and contributes greatly to the formation of a sustainable society. 

1. A polymer represented by Structural Formula (1): [—P₁—R—]_(n)  (1), wherein P₁ is an addition polymer moiety having a continuous hydrocarbon skeleton containing no condensation system and formed by addition polymerization of one or more monomers having a double bond; R is a linking moiety selected from the group consisting of —CONH—, —NH—CO—O—, —NH—CO—NH— and —X₁—A—X₂—, wherein X₁ and X₂ are independently selected from the group consisting of —CONH—, —NH—CO—O— and —NH—CO—NH—, and A is an atomic group capable of linking with X₁ and X₂; and n is a number of repeating units and is an integer of 2 or more, and wherein linkage sites of R represented by a bond between P₁ and R in the repeating unit of the Structural Formula (1) are different between adjacent repeating units.
 2. The polymer according to claim 1, wherein the addition polymer moiety P₁ is at least one moiety selected from the group consisting of polystyrene, polybutadiene, polyacrylonitrile, polyethylene and polypropylene.
 3. A molded article formed by molding the polymer set forth in claim
 1. 4. A process for producing the polymer represented by Structural Formula (1), comprising condensation-polymerizing an addition-polymer having a functional group at each end thereof solely or in a manner of making a two-functional compound intervening therebetween: [—P₁—R—]_(n)  (1), wherein P₁ is an addition polymer moiety having a continuous hydrocarbon skeleton containing no condensation system and formed by addition polymerization of one or more monomers having a double bond; R is a linking moiety for linking plural P₁ and is selected from the group consisting of —CONH—, —NH—CO—O—, —NH—CO—NH— and —X₁—A—X₂—, wherein X₁ and X₂ are independently selected from the group consisting of —CONH—, —NH—CO—O— and —NH—CO—NH—, and A is an atomic group capable of linking with X₁ and X₂; and n is a number of repeating units and is an integer of 2 or more, and wherein linkage sites of R represented by a bond between P₁ and R in the repeating unit of the Structural Formula (1) are different between adjacent repeating units.
 5. The process for producing the polymer according to claim 4, wherein the process further comprises a step of molding the polymer represented by the Structural formula (1). 